1. Field of the Invention
The present invention relates to a control device for a camera unit, and more particularly to a control device for a camera unit, such as a monitoring camera, which is configured to correct a displacement of a preset position, a method of controlling the camera unit, and a program for implementing the control method.
2. Description of the Related Art
Conventionally, there has been known a technique of supporting a camera by an electrically-driven panhead which is capable of performing a pan/tilt operation, and remotely controlling the pan/tilt operation of the electrically-driven panhead, and the focusing, zooming, and like operations of the camera, using control signals from a controller. This technique is applied e.g. to a monitoring camera system. Further, there has been known a function of storing preset positions, including pan/tilt positions, zooming positions, focus positions, in advance, in a memory of a camera, and automatically reproducing one of the preset positions stored in the memory, simply by performing an associated button operation. However, a zoom camera with a high magnification capability suffers from the problem that a preset position is displaced due to an insufficient stopping accuracy of the pan/tilt operation during zooming.
To solve this problem, there has been disclosed a technique in which when registering preset positions, an image (registered-position image) shot when the camera is in each preset position is stored together with information on the preset position (see e.g. Japanese Patent Laid-Open Publication No. 2003-098576). In this technique, when recalling one of the preset positions of the camera, an image (recalled-position image) captured when the camera is in the recalled position and the registered-position image are subjected to image processing to detect an amount of image displacement. Then, the driving of the panhead is controlled based on the detected amount of image displacement such that the camera is moved in the direction of reducing the displacement, whereby the stopping accuracy when recalling the preset position is improved.
In the technique disclosed in Japanese Patent Laid-Open Publication No. 2003-098576, however, if the recalled position image suffers a large amount of displacement from the registered-position image occurs due to an external force applied to the camera by an earthquake or by a contact with a human, it is impossible to correct the displacement of the preset position. Further, it is impossible to correct a displacement of the preset position with a higher accuracy than an accuracy with which the registered-position image is set.